14 results on '"Jae Yoon, Shin"'
Search Results
2. Ancillary Ligand Effects on Heteroleptic Ir III Dye in Dye‐Sensitized Photocatalytic CO 2 Reduction: Photoaccumulation of Charges on Arylated Bipyridine Ligand and Its Control on Catalytic Performance
- Author
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Jae Yoon Shin, Ha-Yeon Cheong, Ho-Jin Son, Sang Ook Kang, Dae Won Cho, Chyongjin Pac, S.J. Choi, Ju Hyoung Jo, and Chul Hoon Kim
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010405 organic chemistry ,Chemistry ,Ligand ,Organic Chemistry ,Photodissociation ,chemistry.chemical_element ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,Catalysis ,0104 chemical sciences ,Turnover number ,Bipyridine ,chemistry.chemical_compound ,Homogeneous ,Photocatalysis ,Iridium - Abstract
Herein, we report the synthesis, and photochemical and -physical properties, as well as the catalytic performance, of a series of heteroleptic IrIII photosensitizers (IrPSs), [Ir(C^N)2 (N^NAryl )]+ , possessing ancillary ligands that are varied with aryl-substituents on bipyridyl unit [C^N=(2-pyridyl)benzo[b]thiophen-3-yl (btp); N^NAryl =4,4'-Y2 -bpy (Y=-Ph or -PhSi(Ph)3 ]. We found that the π-extension of bipyridyl ligand by aryl-substitution put bipyridyl ligand in use as an electron relay unit that performed charge accumulation before delivering to the catalytic center, greatly improving the overall CO2 -to-CO conversion activities. In a typical run, the aryl-substituted IrPS (tBu IrP-PhSi )-sensitized homogeneous systems (IrPS+ReI catalyst) gave a turnover number of 1340 (ΦCO =24.2 %) at the early stage of photolysis (
- Published
- 2020
3. Reversible Symmetry-Breaking Charge Separation in a Series of Perylenediimide Cyclophanes
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Yilei Wu, Michael R. Wasielewski, Jae Yoon Shin, Ryan M. Young, Michelle Chen, Adam F. Coleman, and Jiawang Zhou
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Materials science ,Series (mathematics) ,Charge separation ,business.industry ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Solar energy ,01 natural sciences ,Molecular physics ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,General Energy ,Symmetry breaking ,Physical and Theoretical Chemistry ,0210 nano-technology ,business - Abstract
Excited-state symmetry-breaking charge separation (SB-CS) can offer an efficient pathway to solar energy capture and conversion. We synthesized a series of 1,6,7,12-tetrakis(4-t-butylphenoxy)peryle...
- Published
- 2020
4. Imidazole and 1-Methylimidazole Hydrogen Bonding and Nonhydrogen Bonding Liquid Dynamics: Ultrafast IR Experiments
- Author
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Michael D. Fayer, Yong-Lei Wang, Samantha T. Hung, Steven A. Yamada, and Jae Yoon Shin
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Materials science ,010304 chemical physics ,Hydrogen bond ,Liquid phase ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Liquid dynamics ,chemistry.chemical_compound ,chemistry ,0103 physical sciences ,Materials Chemistry ,Imidazole ,Physical chemistry ,Physical and Theoretical Chemistry ,Polarization (electrochemistry) ,Ultrashort pulse ,1-Methylimidazole - Abstract
The dynamics of imidazole (IM) and 1-methylimidazole (1-MeIM) in the liquid phase at 95 °C were studied by IR polarization selective pump-probe and two-dimensional IR (2D IR) spectroscopies. The two molecules are very similar structurally except that IM can be simultaneously a hydrogen bond donor and acceptor and therefore forms extended hydrogen-bonded networks. The broader IR absorption spectrum and a shorter vibrational lifetime of the vibrational probe, selenocyanate anion (SeCN
- Published
- 2019
5. Water Dynamics in Nanoporous Silica: Ultrafast Vibrational Spectroscopy and Molecular Dynamics Simulations
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Jae Yoon Shin, Steven A. Yamada, Ward H. Thompson, and Michael D. Fayer
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Materials science ,Component (thermodynamics) ,Nanoporous ,Infrared spectroscopy ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Catalysis ,Molecular dynamics ,General Energy ,Water dynamics ,Chemical physics ,Physical and Theoretical Chemistry ,0210 nano-technology ,Ultrashort pulse - Abstract
Nanoporous silica materials are important in catalysis, energy, and materials applications in which water is an essential component. System performance is intimately connected to the water dynamics...
- Published
- 2019
6. Complex Formation and Dissociation Dynamics on Amorphous Silica Surfaces
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Samantha T. Hung, Michael D. Fayer, Steven A. Yamada, and Jae Yoon Shin
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education.field_of_study ,010304 chemical physics ,Relaxation (NMR) ,Population ,010402 general chemistry ,01 natural sciences ,Dissociation (chemistry) ,Standard enthalpy of formation ,0104 chemical sciences ,Surfaces, Coatings and Films ,Silanol ,chemistry.chemical_compound ,Adsorption ,chemistry ,0103 physical sciences ,Materials Chemistry ,Vibrational energy relaxation ,Physical chemistry ,Physical and Theoretical Chemistry ,education ,Benzene - Abstract
Benzene complex formation and dissociation dynamics with silanols on the amorphous silica surfaces of nanoporous SiO2, from a benzene/carbon tetrachloride solution, were measured by the growth of off-diagonal peaks in the two-dimensional infrared (2D IR) chemical exchange spectrum of the isolated Si-OD stretch. The presence of two types of isolated silanols, termed type I and II, was revealed, with dissociation time constants of 82 and 4.0 ps, respectively. The type I silanols are associated with the main IR absorption feature in the Si-OD stretching region, while the type II silanols give rise to a broader shoulder to lower frequency. Polarization selective pump-probe (PSPP) measurements provided the vibrational lifetimes and orientational relaxation rates of the two silanols in the CCl4 (free) and benzene (complex) environments. The type II silanols constitute roughly 30% of the isolated silanol population and exhibit a substantially faster rate of vibrational relaxation, making the type I dynamics the dominant contribution to the PSPP and 2D IR signals. From the measured dissociation times, the enthalpies of formation for the two surface complexes were obtained, with the formation of the type I complex being significantly more exothermic. As the type II site is preferentially removed from the amorphous silica surface with increasing activation temperature, the results provide a reasonable explanation for the increased exothermicity of benzene adsorption on silica with increasing activation temperature in previous calorimetry experiments.
- Published
- 2021
7. Influence of Vibronic Coupling on Ultrafast Singlet Fission in a Linear Terrylenediimide Dimer
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Jonathan D. Schultz, Mark A. Ratner, Michael R. Wasielewski, Michelle Chen, Jae Yoon Shin, Ryan M. Young, and James P. O’Connor
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Chemistry ,Dimer ,General Chemistry ,Chromophore ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Molecular physics ,Catalysis ,0104 chemical sciences ,symbols.namesake ,chemistry.chemical_compound ,Vibronic coupling ,Colloid and Surface Chemistry ,Excited state ,Singlet fission ,symbols ,Molecule ,Singlet state ,Hamiltonian (quantum mechanics) - Abstract
Singlet fission (SF) is a photophysical process capable of boosting the efficiency of solar cells. Recent experimental investigations into the mechanism of SF provide evidence for coherent mixing between the singlet, triplet, and charge transfer basis states. Up until now, this interpretation has largely focused on electronic interactions; however, nuclear motions resulting in vibronic coupling have been suggested to support rapid and efficient SF in organic chromophore assemblies. Further information about the complex interactions between vibronic excited states is needed to understand the potential role of this coupling in SF. Here, we report mixed singlet and correlated triplet pair states giving rise to sub-50 fs SF in a terrylene-3,4:11,12-bis(dicarboximide) (TDI) dimer in which the two TDI molecules are covalently linked by a direct N-N connection at one of their imide positions, leading to a linear dimer with perpendicular TDI π systems. We observe the transfer of low-frequency coherent wavepackets between the initial predominantly singlet states to the product triplet-dominated states. This implies a non-negligible dependence of SF on nonadiabatic coupling in this dimer. We interpret our experimental results in the framework of a modified Holstein Hamiltonian, which predicts that vibronic interactions between low-frequency singlet modes and high-frequency correlated triplet pair motions lead to mixing of the pure basis states. These results highlight how nonadiabatic mixing can shape the complex potential energy landscape underlying ultrafast SF.
- Published
- 2021
8. Tuning the charge transfer character of the multiexciton state in singlet fission
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Ryan M. Young, Michael R. Wasielewski, Michelle Chen, and Jae Yoon Shin
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Physics ,010304 chemical physics ,Exciton ,General Physics and Astronomy ,Charge (physics) ,010402 general chemistry ,01 natural sciences ,Molecular physics ,0104 chemical sciences ,Electron transfer ,Intramolecular force ,0103 physical sciences ,Singlet fission ,Ultrafast laser spectroscopy ,Physical and Theoretical Chemistry ,Spin (physics) ,Spectroscopy - Abstract
Intramolecular singlet fission (SF) produces the multiexciton correlated triplet pair state, (T1T1), prior to the formation of free triplet excitons. The nature of the multiexciton state is complex, as generation of the (T1T1) state may involve a charge transfer (CT) intermediate and has been shown to have both mixed electronic and spin characters. According to transient absorption spectroscopy, a linear terrylene-3,4:11,12-bis(dicarboximide) dimer (TDI2) exhibits solvent-dependent excited-state dynamics. As solvent polarity increases from 1,2,4-trichlorobenzene (e = 2.2) to chlorobenzene (e = 5.6) to 1,2-dichlorobenzene (e = 9.9), the SF rate in TDI2 increases and the multiexciton state, which can be thought of as a linear combination of the 1(S1S0), CT, and (T1T1) states, gains more CT character. Eventually, the CT state becomes a trap state as indicated by symmetry-breaking charge separation in TDI2 in pyridine (e = 12.3). The dielectric environment influences not only the SF rate and the relative contributions of the 1(S1S0), CT, and (T1T1) states to the overall multiexciton state but also the rate at which the state mixing evolves, with faster dynamics in higher polarity solvents. More importantly, the tunability and presence of strong CT character in the multiexciton state have implications for SF applications since they often rely on electron transfer from the free triplet excitons. This enhanced CT character in the (T1T1) state may assist with two-electron transfer directly from the (T1T1) state, allowing for facile extraction of charges in intramolecular SF systems whose (T1T1) states do not always efficiently dissociate to two triplet excitons.
- Published
- 2020
9. Steric Interactions Impact Vibronic and Vibrational Coherences in Perylenediimide Cyclophanes
- Author
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Jae Yoon Shin, Aritra Mandal, Jonathan D. Schultz, Michael R. Wasielewski, Ryan M. Young, Mark A. Ratner, and Adam F. Coleman
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Physics ,Steric effects ,010405 organic chemistry ,Molecular systems ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,symbols.namesake ,Chemical physics ,symbols ,General Materials Science ,Physical and Theoretical Chemistry ,van der Waals force ,Coherence (physics) - Abstract
Designing molecular systems that exploit vibronic coherence to improve light harvesting efficiencies relies on understanding how interchromophoric interactions, such as van der Waals forces and dipolar coupling, influence these coherences in multichromophoric arrays. However, disentangling these interactions requires studies of molecular systems with tunable structural relationships. Here, we use a combination of two-dimensional electronic spectroscopy and femtosecond stimulated Raman spectroscopy to investigate the role of steric hindrance between chromophores in driving changes to vibronic and vibrational coherences in a series of substituted perylenediimide (PDI) cyclophane dimers. We report significant differences in the frequency power spectra from the cyclophane dimers versus the corresponding monomer reference. We attribute these differences to distortion of the PDI cores from steric interactions between the substituents. These results highlight the importance of considering structural changes when rationalizing vibronic coupling in multichromophoric systems.
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- 2019
10. Influence of Water on Carbon Dioxide and Room Temperature Ionic Liquid Dynamics: Supported Ionic Liquid Membrane vs the Bulk Liquid
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Michael D. Fayer, Steven A. Yamada, and Jae Yoon Shin
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Materials science ,010304 chemical physics ,Infrared ,Diffusion ,Analytical chemistry ,Ether ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,chemistry.chemical_compound ,Membrane ,chemistry ,0103 physical sciences ,Carbon dioxide ,Ionic liquid ,Materials Chemistry ,Physical and Theoretical Chemistry ,Polarization (electrochemistry) ,Imide - Abstract
The influence of water on the dynamics of a room temperature ionic liquid (RTIL), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EmimNTf2), and CO2 in the RTIL was studied in the bulk liquid and a supported ionic liquid membrane (SILM) using two-dimensional infrared (IR) and IR polarization selective pump–probe spectroscopies. In the water-saturated bulk EmimNTf2, the complete orientational randomization and structural spectral diffusion (SSD) of CO2 became faster than in the dry EmimNTf2. In the poly(ether sulfone) SILM, only the longer time components of the SSD became faster in the water-saturated RTIL; the complete orientational randomization remained similar to the dry RTIL in the SILM. The implication is that the presence of water in EmimNTf2 contained in the SILM facilitates the fluctuation of globally modified RTIL structure in the pores, but the local RTIL environments are relatively unaffected.
- Published
- 2018
11. Carbon Dioxide in a Supported Ionic Liquid Membrane: Structural and Rotational Dynamics Measured with 2D IR and Pump–Probe Experiments
- Author
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Michael D. Fayer, Steven A. Yamada, and Jae Yoon Shin
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chemistry.chemical_classification ,Infrared ,Analytical chemistry ,Ether ,02 engineering and technology ,General Chemistry ,Polymer ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Sulfone ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Membrane ,chemistry ,Ionic liquid ,0210 nano-technology ,Polarization (electrochemistry) ,Imide - Abstract
Supported ionic liquid membranes (SILMs) are porous membranes impregnated with ionic liquids (ILs) and used as advanced carbon capture materials. Here, two-dimensional infrared (2D IR) and IR polarization selective pump–probe (PSPP) spectroscopies were used to investigate CO2 reorientation and spectral diffusion dynamics in SILMs. The SILM contained 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonly)imide in the poly(ether sulfone) membrane with average pore size of ∼350 nm. Two ensembles of CO2 were observed in the SILM, one in the IL phase in the membrane pores and the other in the supporting membrane polymer. CO2 in the polymer displayed a red-shifted IR absorption spectrum and a shorter vibrational lifetime of the asymmetric stretch mode compared to the IL phase. Despite the relatively large pore sizes, the complete orientational randomization of CO2 and structural fluctuations of the IL (spectral diffusion) in the pores are slower than in the bulk IL by ∼2-fold. The implication is that the IL st...
- Published
- 2017
12. First Evidence of Vibrationally Driven Bimolecular Reactions in Solution: Reactions of Br Atoms with Dimethylsulfoxide and Methanol
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Jae Yoon Shin, Michael A. Shaloski, Amanda S. Case, and F. Fleming Crim
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Bromine ,010304 chemical physics ,Chemistry ,Photodissociation ,chemistry.chemical_element ,Hydrogen atom ,010402 general chemistry ,Photochemistry ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Solvent ,symbols.namesake ,0103 physical sciences ,Atom ,Ultrafast laser spectroscopy ,Materials Chemistry ,symbols ,Molecule ,Physical and Theoretical Chemistry ,van der Waals force - Abstract
We present evidence for vibrational enhancement of the rate of bimolecular reactions of Br atoms with dimethylsulfoxide (DMSO) and methanol (CH3OH) in the condensed phase. The abstraction of a hydrogen atom from either of these solvents by a Br atom is highly endoergic: 3269 cm–1 for DMSO and 1416 or 4414 cm–1 for CH3OH, depending on the hydrogen atom abstracted. Thus, there is no thermal abstraction reaction at room temperature. Broadband electronic transient absorption shows that following photolysis of bromine precursors Br atoms form van der Waals complexes with the solvent molecules in about 5 ps and this Br•–solvent complex undergoes recombination. To explore the influence of vibrational energy on the abstraction reactions, we introduce a near-infrared (NIR) pump pulse following the photolysis pulse to excite the first overtone of the C—H (or O—H) stretch of the solvent molecules. Using single-wavelength detection, we observe a loss of the Br•–solvent complex that requires the presence of both photo...
- Published
- 2017
13. Dynamics of a Room Temperature Ionic Liquid in Supported Ionic Liquid Membranes vs the Bulk Liquid: 2D IR and Polarized IR Pump–Probe Experiments
- Author
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Steven A. Yamada, Jae Yoon Shin, and Michael D. Fayer
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Chemistry ,Infrared ,Diffusion ,Triatomic molecule ,Analytical chemistry ,Ether ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Ion ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Membrane ,Ionic liquid ,Organic chemistry ,0210 nano-technology ,Polarization (electrochemistry) - Abstract
Supported ionic liquid membranes (SILMs) are membranes that have ionic liquids impregnated in their pores. SILMs have been proposed for advanced carbon capture materials. Two-dimensional infrared (2D IR) and polarization selective IR pump–probe (PSPP) techniques were used to investigate the dynamics of reorientation and spectral diffusion of the linear triatomic anion, SeCN–, in poly(ether sulfone) (PES) membranes and room-temperature ionic liquid (RTIL), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EmimNTf2). The dynamics in the bulk EmimNTf2 were compared to its dynamics in the SILM samples. Two PES membranes, PES200 and PES30, have pores with average sizes, ∼300 nm and ∼100 nm, respectively. Despite the relatively large pore sizes, the measurements reveal that the reorientation of SeCN– and the RTIL structural fluctuations are substantially slower in the SILMs than in the bulk liquid. The complete orientational randomization, slows from 136 ps in the bulk to 513 ps in the PES30. 2D IR...
- Published
- 2016
14. Comparative Study of Cl-Atom Reactions in Solution Using Time-Resolved Vibrational Spectroscopy
- Author
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F. Fleming Crim, Amanda S. Case, and Jae Yoon Shin
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010304 chemical physics ,Chemistry ,Infrared spectroscopy ,010402 general chemistry ,Photochemistry ,Branching (polymer chemistry) ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Reaction rate ,Solvent ,Reaction rate constant ,Excited state ,0103 physical sciences ,Materials Chemistry ,Physical and Theoretical Chemistry ,Excitation - Abstract
A Cl atom can react with 2,3-dimethylbutane (DMB), 2,3-dimethyl-2-butene (DMBE), and 2,5-dimethyl-2,4-hexadiene (DMHD) in solution via a hydrogen-abstraction reaction. The large exoergicity of the reaction between a Cl atom and alkenes (DMBE and DMHD) makes vibrational excitation of the HCl product possible, and we observe the formation of vibrationally excited HCl (v = 1) for both reactions. In CCl4, the branching fractions of HCl (v = 1), Γ (v = 1), for the Cl-atom reactions with DMBE and DMHD are 0.14 and 0.23, respectively, reflecting an increased amount of vibrational excitation in the products of the more exoergic reaction. In addition, Γ (v = 1) for both reactions is larger in the solvent CDCl3, being 0.23 and 0.40, as the less viscous solvent apparently dampens the vibrational excitation of the nascent HCl less effectively. The bimolecular reaction rates for the Cl reactions with DMB, DMBE, and DMHD in CCl4 are diffusion limited (having rate constants of 1.5 × 10(10), 3.6 × 10(10), and 17.5 × 10(10) M(-1) s(-1), respectively). In fact, the bimolecular reaction rate for Cl + DMHD exceeds a typical diffusion-limited reaction rate, implying that the attractive intermolecular forces between a Cl atom and a C═C bond increase the rate of favorable encounters. The 2-fold increase in the reaction rate of the Cl + DMBE reaction from that of the Cl + DMB reaction likely reflects the effect of the C═C bond, while both the number of C═C bonds and the molecular geometry likely play a role in the large reaction rate of the Cl + DMHD reaction.
- Published
- 2016
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